Process of making thymol



Patented July 24, 1934 PROCESS OF MAKING THYMOL Walter J. Hund, San Francisco, Calif.

No Drawing. Application April 28, 1930, Serial No. 448,183

3 Claims. (Cl. 260-454) This invention deals with the production of thymol, a substance useful as a reagent and, med-iei-nally, as an antiseptic. The invention relates further to the production of thymol from 5 umbellulone, ClOHMO, 3 ketone alpha thujene and, more particularly, to the production of thymol from an essential oil as California laurel oil which contains umbellulone. This application is a continuation in part of my application Serial No. 171,377, filed. February 26, 1927.

Heretofore it has been judged necessary to conduct the conversion of umbellulone into thymol by treating the crude laurel oil to secure a fraction of pure umbellulone and by continuing the heating of the pure umbellulone for a relatively long period of time. Thus Semmler in the Berichte Der Deutschen Chemischen Gesell schaft, Vol. 41, part III, pages 3993-3994 sets forth a process by which pure umbellulone was secured from laurel oil and this pure umbellulone was isomerized to thymol by heating the pure umbellulone in a sealed bomb tube for a period of eighteen hours at a temperature of about 280 C. I have discovered that it is not necessary to employ a pure umbellulone fraction and that the length of time for the conversion heretofore deemed necessary was not in fact so. Thus I have found that the conversion of umbellulone into thymol can be successfully consummated in a much shorter period of time. Thus, in one conversion which I have conducted, I placed laurel oil containing umbellulone in a vessel or autoclave and heated the autoclave to a temperature above the boiling point of thymol 232 C. (231.8 C.) which temperature I maintained for approximately one hour, the umbellulone containing oil being under the pressure resulting from the temperature. At the end of the hour it was found that the umbellulone had been substantially entirely converted into thymol.

I prefer that the reaction be conducted in the liquid phase and to this end employ preferably an autoclave which, as is well known in the art, is a vessel which can be sealed and is capable of withstanding a relatively high pressure. The temperature employed preferably ranges above the boiling point of thymol since the isomerization occurs very slowly below this temperature and, also, preferably below a temperature at which the decomposition of the material in the autoclave will occur. In this connection I have found it unnecessary to heat the liquid above 300 C. while I have successfully conducted the conversion at temperatures between the boiling point of thymol and 300 0., the optimum temperature being 280 C. The conversion to thymol occurssubstantia'lly quantitatively in about an hour and complete isomerization is usually effected in less than two hoursof heating.

After the essential oil has been subjected to the temperature and pressure for sufficient time to complete isomerization, the liquid is permitted to cool and is discharged from the autoclave. The converted oil can be used as it is or the thymol can be allowed to crystallize out and sep- 66 arate from the oil. The thymol content may also be completely extracted by other well known chemical methods as distillation or extraction with an aqueous solution of a caustic alkali and treating this extract to secure the 10 thymol as by adding an acidsee Nelson Patent 1,666,342.

As a preferred source of the material I preferably utilize the essential oil obtained by steam distillation of the leaves, branches and wood of the tree which is popularly known as California laurel and scientifically as Umbellularia californice or Oreodaplme californica. This tree grows widely in the coast ranges of California and Oregon. The term laurel oil, as used herein and in the claims, is intended to include the oil as recovered from the laurel or other source and also fractions thereof which are procured by fractionation to effect a concentration in the umbellulone content.

The essential oil obtained upon steam distillation in the usual manner contains, in addition to the umbellulone, substantial amounts of pinene, phellandrene, cineol and other constituents. The essential oil as obtained by steam distillation, can be directly evaluated for its possible thymol content, I have found, by subjecting it to the treatment I have previously outlined, or the raw oil may be subjected to fractional distillation. In this connection I have found that the fraction taken below 200 C., and which usually comprises up to 50% of the raw oil contains a large percentage of cineol and may be readily evaluated in this respect. The fraction taken above 200 C. holds the irritating components of the raw oil as well as the umbellulone. This fraction or the raw oil can be treated, if desired, to convert the disagreeable and difiicultly isolatable umbellulone into the valuable and easily isolatable thymol. I have I05 observed that the other constituents such as cineol, phellandrene, pinene are not affected by the isomerization treatment when it is conducted under the conditions which I have outlined.

By discovering that the umbellulone fraction of the essential oil of California laurel or laurel oil, can be successfully converted into thymol by heating in the liquid phase at a temperature sufficient to convert the umbellulone into thymol without any substantial decomposition, the commercial utilization of this essential oil has been facilitated since it is no longer necessary to conduct the heating process-over the long period heretofore deemed necessary and of which Semmler is representative further, it is not necessary to carry out the refining of the umbellulone before evaluation as thymol as is taught by Semmler. Also, the irritating and difiicultly handled umbellulone is converted into the valuable thymol which can be isolated readily thus facilitating subsequent evaluation of the other constituents which are present.

I claim:

1. The process of effecting an evaluation as thymol of the umbellulonecontent of California laurel, oil which comprises securing the laurel oil containing umbellulone and other laurel oil constituents, subjecting the laurel oil to a temperature of about 280 C. and under substantially the vapor pressure of the laurel oil at substantially that temperature for a period sufficient to convert the umbellulone into thymol, and substantially recovering the thymol thus formed from the remaining laurel oil constituents.

3. The step in a process of treating laurel oil which consists in subjecting laurel oil to a temperature of about 280 C. and the vapor pressure of said laurel oil at that temperature for about one hour.

WALTER J .HUND, 

